The studies in the present proposal will deal with the active regulatory mechanisms for control of H plus in the brain and CSF because the H plus in central chemoreceptors is a major determinant of alveolar ventilation. The studies will utilize anesthetized dogs and evaluate the role of organic buffers and ammonia in the CNS in control of H plus. The factors determining the CSF H plus will be assessed in respiratory acidosis and alkalosis from the standpoint of the brain metabolic activity and the relationship to alterations in plasma bicarbonate. Site and mechanism of action of ammonia as a central respiratory stimulant will also be studied.